Hope Hicks, US President, Donald Trump’s communications director and one of his longest-serving associates, resigned a day after she was grilled on the Russian meddling in 2016 US polls.

A file shows Hope Hicks arriving at Trump Tower for meetings with Donald Trump in New York. (AFP File Photo)

Hope Hicks, US President Donald Trump’s communications director and one of his longest-serving associates, on Wednesday announced she was resigning, adding to the long line of senior aides who have exited the White House in just over 13 months of its term.

Hicks cited no reasons for leaving, but the timing did raise questions, as her resignation came just a day after she told a congressional panel investigating Russian meddling in 2016 US polls, that she has had to tell “white lies” while serving the President. She was grilled for nine hours in the closed-door hearing.

She is the fourth communications director to leave Trump following Michael Dubke, Sean Spicer and Anthony Scaramucci. Other senior aides to have left include chief of staff Reince Priebus, chief strategist Steve Bannon, NSA Michael Flynn and deputy NSA Dina Powell.

A former model, Hicks, who is only 29, had worked with Trump the longest, starting in the Trump Organization before he announced his candidacy. She was generally thought to know the President’s mind the best, and could push back and challenge him.

“She is as smart and thoughtful as they come, a truly great person,” Trump said in a statement, adding, “I will miss having her by my side, but when she approached me about pursuing other opportunities, I totally understood.”

In a separate statement, Hicks said, “There are no words to adequately express my gratitude to President Trump. I wish the President and his administration the very best as he continues to lead our country.”

She is expected to leave in few weeks, the White House said. A replacement is yet to be named.

Despite her proximity to the President, Hicks had kept an unusually low-profile, first as an aide on the campaign team, and then in the White House. She never gave interviews or addressed news briefings, as usually done by communications directors.

She had joined the White House as an “an unconventional press and communications aide”, an official said, and her role evolved when she was “formally being announced WH communications director in the summer of 2017” after Scaramucci’s short-lived 11-day term.

In that role, Hope led “strategic messaging for administration priorities such as the historic passage of tax reform and worked with Press Secretary Sarah Sanders to stabilize the press and communications teams after initial phases of transition”.

She also faced scrutiny and criticism for helping the President write a misleading first official response to reports about his son Donald Trump Jr’s meetings with Russians in the Trump Tower in New York during the campaign, to explore their offer of political dirt on Hillary Clinton.

And more recently, she faced criticism for framing the White House’s defence of senior aide Rob Porter — whom she was dating at the time — against allegations he had assaulted his two former wives. Porter had to quit.

Corey Lewandowski, the first head of Trump’s campaign, called Hicks “smart and private, with nearly a photographic memory” in a book he co-authored about the campaign. She came to the campaign while she was working with Ivanka Trump on one of her fashion lines and on some Trump Organization resorts.